Cardiac Muscle - Cells, Structure and Function

Question 1

Cell types of the heart

Answer 1

1. Contractile (CMs)
2. Conduction cells
3. Endothelial cells (capillaries)
4. Fibroblasts

Question 2

Fibroblasts

Answer 2

• Small but numerous (2/3 of cell number)

- Form the ECM, an inter-cell collagen network

Question 3

Surrounding each CM

Answer 3

• At least one fibroblast

- At least 2 capillaries

Question 4

4 key cytoskeletal elements of the Sarcomere

Answer 4

1. Titin
2. The M-band
3. The Z-disc
4. MyBP-C

Question 5

Titin

Answer 5

• Extends from z-disc to M-band
• Associated with thick filament in the A-band but runs free in the I-band
• Forms template for synthesis of thick filament
• Helps make muscle more elastic
• Prone to mutations due to its long length

Question 6

The M-Band

Answer 6

• Cross-links the thick filament into a hexagonal lattice

- A-band becomes disordered in contraction, re-ordered by the elasticity of the M-band

Question 7

The Z-disc

Answer 7

• Opposite polarity actin filaments overlap here

- a-actinin cross-links the filaments

Question 8

MyBP-C

Answer 8

• Role is slightly unclear
• When PKA Pi-lates it, stretch-activation occurs faster
• Large protein that binds thick filament and may help binding of